The presence of turfgrass in a landscape directly impacts the quality of human life from a visual, functional and recreational point of view. In the United States, there are currently greater than 12 million hectares of turfgrass including lawns, parks, golf courses, sod farms, industrial and institutional grounds, and highway right-of ways. In New York State alone, over 3.4 million hectares have been established in turfgrass. In all turf settings, especially lawn and roadside turf, weeds are a key pest problem. A substantial pesticide market (over two billion U.S. dollars) currently exists for control of weeds, insects, and diseases in private and commercial turfgrass settings in the United States. Although herbicides continue to be the predominant form of weed management in commercial turf settings, herbicide use in public and private landscapes is increasingly challenged by environmental and health concerns (Mortensen et al., “The Role of Ecology in the Development of Weed Management Systems: An Outlook,” Weed Res. 40:49-62 (2000)). Consequently, turfgrass stakeholders, including homeowners and turf managers, are seeking alternative weed management tools (Matteson, P., “The ‘50% Pesticide Cuts’ in Europe: a Glimpse of Our Future?,” Am. Entomol. 41:210-220 (1995). One preventive strategy to minimize weed infestation is the use of appropriate turf mixtures or cultivars that are well adapted to a given setting. Weeds are much less likely to invade a well managed turf in optimal condition, maintained with appropriate cultural practices including timely mowing, fertilization, and irrigation (Bertin, “Alternate Weed Management Strategies for Landscape and Turf Settings,” in Inderjit, Ed., Weed Biology and Management, Dordrecht/Boston/London: Kluwer Academic Publishers, pp. 403-422 (2004)).
Biological and organic approaches for weed management in turf have often not provided effective long-term control of turf weeds (Bertin, “Alternate Weed Management Strategies for Landscape and Turf Settings,” in Inderjit, Ed., Weed Biology and Management, Dordrecht/Boston/London: Kluwer Academic Publishers, pp. 403-422 (2004)). Although plant pathogenic organisms have been evaluated for selective control of turf weeds, few, if any, commercial biocontrol products for weed management are currently available. Evaluation of organic products for weed management in turf has shown that most products do not provide selective, or cost-effective long-term weed suppression. Weed removal by mulching, cultivation, flame-burning, and steaming can be utilized in landscapes, but is cost prohibitive and sometimes injurious to turf (Bertin, “Alternate Weed Management Strategies for Landscape and Turf Settings,” in Inderjit, Ed., Weed Biology and Management, Dordrecht/Boston/London: Kluwer Academic Publishers, pp. 403-422 (2004); Weston L. A., “Developing Natural Pest Control Products for Turf,” Cornell University Turfgrass Times pp. 1-7 (1999)). Organic products such as acetic acid or clove oil-based products will result in significant turf injury. Corn gluten meal can provide some initial preemergent weed suppression but many studies have shown inconsistent control (Bertin, “Alternate Weed Management Strategies for Landscape and Turf Settings,” in Inderjit, Ed., Weed Biology and Management, Dordrecht/Boston/London: Kluwer Academic Publishers, pp. 403-422 (2004)).
Weed management in turfgrass settings. Weed infestation often leads to lower crop yields in agriculture, less efficient land use, and poor crop quality (Ashton et al., “Weed Science Principles and Practices,” Third Edition (1991)). In agronomic crops, specific problems caused by weedy plants constitute several billion dollars of annual yield loss in the United States alone. The green industry, including private and commercial landscape projects such as golf courses, parks, and athletic fields has experienced significant expansion over the last decade. In a typical city in the United States, 70% of the total turfgrass acreage consists of residential lawns (Cockerham et al., “The Size, Scope, and Importance of the Turfgrass Industry,” in Gibeault et al., Eds., Turfgrass Water Conservation, University of California, Riverside: Division of Agriculture and Natural Resources, pp. 7-12 (1985)). In turfgrass settings, the traditional definition of a weed is often expanded to any plant that is unwanted because of its disruptive effect on the aesthetic appearance, stabilizing capacity, or overall utility of a turf (Turgeon, A. J., “Turfgrass Management,” Upper Saddle River, N.J.: Charles Stewart, 356 p. (1996)). Uniformity is one of the key components of turfgrass quality. A different leaf width and/or shape, growth habit, or color will substantially disrupt the uniformity of a turf (Beard, J. B., “Turfgrass: Science and Culture,” Englewood Cliffs, N.J.: Prentice Hall (1973)). In addition to detracting from aesthetic appearance and uniformity, weeds also compete with desirable turfgrass species for light, soil moisture and nutrients, and carbon dioxide (Beard, J. B., “Turfgrass: Science and Culture,” Englewood Cliffs, N.J.: Prentice Hall (1973)).
Weed management in turfgrass settings is generally limited to those methods involving prevention of propagule dispersal and those limiting infestation including mechanical and chemical controls (Beard, J. B., “Turfgrass: Science and Culture,” Englewood Cliffs, N.J.: Prentice Hall (1973)). Sanitary practices resulting in prevention of infestation include the use of weed free sod, soil and sand, equipment cleaning to remove propagules and mowing of weed-infested adjacent fields to prevent weed seed dispersal. Weed encroachment into an established turf is minimized when appropriate management practices create a dense, vigorous sward. Utilization of the proper turf species, mowing height and frequency, soil fertility and pH level, irrigation frequency and intensity, disease, insect and nematode controls, and aeration of compacted areas can result in a dense and vigorous turf. Mechanical weed control in turf, including removal of weeds either by hand or by spading, is a labor intensive control method, even though it can be effectively used for broadleaf weeds on relatively small turf areas (Beard, J. B., “Turfgrass: Science and Culture,” Englewood Cliffs, N.J.: Prentice Hall (1973)).
Pest management in green settings can be intensive as zero tolerance for pests is often the case, with multiple applications of herbicides utilized to manage weeds. Concerns over the long-term effects of synthetic chemicals in agriculture and the green industry have led to research focused on the discovery of natural products for pest management and development of alternative pest management strategies based on biological control for landscape and turf settings (Bertin et al., “Alternate Weed Management Strategies for Landscape and Turf Settings,” In derjit, in Weed Biology and Management, Inderjit, Ed., Dordrecht/Boston/London: Kulwer Academic Publishers, pp. 403-422 (2004); Cardellina, J. H., “Natural Products in the Search for New Agrochemicals,” in Cutler., H. G., Ed., Biologically Active Natural Products: Potential Use in Agriculture, Washington, D.C.: American Chemical Society, pp. 305-315 (1988); Duke, S. O., “Weeding with Transgenes,” Trends Biotech. 21:192-195 (2003)). Turf industry officials need to stay apprised of efforts to impose non-chemical or organic maintenance protocols as well as the science and regulations concerning pesticide use. The United States Golf Association (USGA) has invested $25 million in turfgrass and environmental research since 1983, much of which has focused on the development of turfgrass species requiring less pesticide, fertilizer, and water, and best management practices aimed at reducing risk to the environment. Chemical manufacturers have also continued to develop reduced-risk products for safer alternatives to many older pesticides. The development of alternative products and holistic management solutions presents some exciting opportunities and challenges for agricultural science researchers.
Alternative Weed Management Strategies. The use of pathogenic organisms to control weeds has not proven particularly effective due to problems in obtaining consistent control and difficulty in developing the appropriate mode of release for biocontrol organisms (Bertin et al., “Laboratory Assessment of the Allelopathic Effects of Fine Leaf Fescues,” J. Chem. Ecol. 29:1919-1937 (2003)). Certain biological agents such as viruses, bacteria and fungi can selectively kill the target weed without injuring the turf. The likelyhood of finding organisms with both the selectivity and the ability to be stored for long-term periods of time for use as commercial herbicides are small. One organism that has recently received great attention in the turf industry is Xanthomonas campestris pv. poannua. This bacterium selectively controls annual bluegrass (Poa annua L.), a serious weed in managed turfgrass stands, including golf courses. The main limitations of the formulated product containing the bacteria are its short shelf life and the fact that it appears to work better on annual biotypes of Poa than on the more abundant perennial types. Working with living organisms requires the development of specific techniques for successful application and control. Research has been conducted to scale up production of X. campestris as well as determination of appropriate storage conditions (Jackson et al., “Growth Requirements for Production of Stable Cells of the Bioherbicidal Bacterium Xanthomonas campestris,” J. Ind. Microb. Biotech. 21:237-241 (1998)).
The use of natural products as bioherbicides for weed control is also receiving increased attention (Duke et al., “Chemicals From Nature for Weed Management,” Weed Sci. 50:138-151 (2002); Duke et al., “Strategies for the Use of Natural Products for Weed Management,” J. Pesticide Sci. 27:298-306 (2002)). In 1984, Rice, E. L., “Allelopathy,” Orlando: Academic Press, xi, 422 p. (1984) suggested that the use of plant-derived compounds as natural herbicides is an environmentally-sound option for weed management. Recently, corn or wheat gluten meal has been studied for use as a preemergent bioherbicide for turf and landscape settings (Bingamen et al., “Greenhouse Screening of Corn Gluten Meal as a Natural Control Product for Broadleaf and Grassy Weeds,” Hort. Sci. 30:1256-1259 (1995); Gough et al., “Wheat Gluten Meal Inhibits Germination and Growth of Broadleaf and Grassy Weeds,” HortSci. 34:269-270 (1999); Unruh et al., “Herbicidal Effects of the Dipeptide Alanyl-Alanine on Perennial Ryegrass (Lolium perenne L.) Seedlings,” Crop Sci. 37:208-211 (1997)).
Corn gluten meal contains 10% nitrogen by weight, a relatively high percentage of available nitrogen. It is a pre-emergent material only and has no post-emergent effects on weeds that are already established. Corn gluten meal could be considered as a natural weed-and-feed material for turf, as it purportedly inhibits the establishment of germinating weeds while acting as a fertilizer. Radicle damage in germinating weed seed appears to be localized to the meristematic region resulting in inhibition of root elongation. Among the weeds reportedly controlled with pre-emergent applications of the product are crabgrass (Digitaria sp.), dandelion (Taraxacum officinale W.), smartweed (Polygonum sp.), redroot pigweed (Amaranthus retroflexus L), purslane (Portulaca oleracea L), lambsquarters (Chenopodium album L), foxtail (Setaria sp.), and barnyardgrass (Echinochloa crus-galli (L.) Beauv) (Gough et al., “Wheat Gluten Meal Inhibits Germination and Growth of Broadleaf and Grassy Weeds,” HortSci. 34:269-270 (1999)). Both powder and pelleted formulations are available.
In turf situations, corn gluten meal is often applied at 20 lb/1000 square feet (Gough et al., “Wheat Gluten Meal Inhibits Germination and Growth of Broadleaf and Grassy Weeds,” HortSci. 34:269-270 (1999)). Potential problems with corn gluten meal can arise, depending on the availability of soil moisture and microbial activity, both of which reduce product efficacy. The other drawback is the higher cost of corn gluten meal as compared to other standard fertilizers and weed and feed products. The generally low specific activity of the active ingredients associated with corn gluten meal including alaninyl-alanine, a dipepetide isolated from corn gluten meal, may also lead to inconsistent results in field applications. Sensitive species purportedly exhibit damage to cellular membranes, altered cell nuclei and mitotic structures, and an overall loss of cytoplasmic integrity. Treated root tips were reported to exhibit extreme cell wall abnormalities including uneven thickening and breakage, especially in the epidermal and subepidermal cells (Unruh et al., “Mitotic and Ultrastructure Changes in Root Merestems of Grass Seedlings Treated with Alaninyl-Alanine,” Crop Sci. 37:1870-1874 (1997)).
The present invention is directed to overcoming these and other deficiencies in the art.